Understanding how ancient species arranged themselves in space is a key puzzle in paleoecology, but direct evidence of how prehistoric organisms used their body structures to regulate spacing has long eluded scientists. Now, researchers in China have uncovered the first direct evidence: Approximately 436-million-year-old brachiopods from the early Silurian period used tiny, bristle-like structures called setae to maintain orderly, “checkerboard” spacing—ensuring they had enough room to thrive on the ancient seafloor.